Friday, December 7, 2012

This post is one of a series from professor Nisse Goldberg's Plant
Taxonomy students at Jacksonville University. FNPS blogger Laurie
Sheldon assisted the students with their initial drafts, providing
suggestions for editing and content development.

Description
The cactus plant family or
Cactaceae is specially adapted to survive in hot and dry conditions. For
example, many species have sharp spines to protect them from predation,
direct rain runoff towards their root system, and reduce internal heat
loading by reflecting light away from the plant (Fig. 1). In addition,
the dermal cells are thick-walled and lined with a cuticle or waxy
layer. The cuticle helps the plant retain water and to reflect light,
thereby reducing internal temperatures.

Photosynthesis, the production of sugars, commonly occurs in the leaves
of most plants. As the majority of species in the cactus family have
reduced leaves, they conduct photosynthesis primarily along their stems
or areoles. These shoots are also where the cactus retains its water,
expanding and contracting to accommodate the changing quantities of
water being absorbed from the roots.

The
root system of the cactus remains relatively close to the surface while
extending out up to 15 meters! During heavy amounts of precipitation,
the roots will begin to grow new root extending from the previous roots
to increase water absorption. During times of drought the roots will
begin to shrivel and deteriorate creating an air gap that can help trap
water.

There are 23 species of Cactaceae in Florida, 12 of which are native.
Among the native species, 7 are listed by the state as endangered.
Examples of these include Opuntia corrallicola, semaphore pricklypear, and Harrisia fragrans, Caribbean applecactus (Figs. 1 and 2). Found in Texas, Peyote or Lophophora williamsii is known for psychoactive effects (Fig. 3).